Up to 30 drill music videos from U.K. rap artists have been removed from YouTube following complaints from the Metropolitan police of London that the videos reportedly incite violence.

According to a report from The Guardian, U.K. police believe gangs are using the videos to threaten each other. “The gangs try to outrival each other with the filming and content—what looks like a music video can actually contain explicit language with gangs threatening each other,” Mike West of the Metropolitan police told BBC. “There are gestures of violence, with hand signals suggesting they are firing weapons and graphic descriptions of what they would do to each other”

U.K. drill music is based off of the style of rap which originated in Chicago in the early 2010s with artists such as Chief Keef and King Louie. Police now believe the popularity of drill music in the U.K. is responsible for the rise in gang violence across London.

“Drill music is associated with lyrics which are about glamorizing serious violence: murder, stabbings,” Metropolitan police commissioner, Cressida Dick told LBC radio. “They describe the stabbings in great detail, joy and excitement. Extreme violence against women is often talked about.”

While police asked YouTube to take down 50 to 60 music videos, the website is believed to have removed around 30 videos, although police say they have a database of more than 1,400 videos they can use as an attempt to reduce violent crime.

“We have developed policies specifically to help tackle videos related to knife crime in the UK and are continuing to work constructively with experts on this issue,” a spokesperson for YouTube said. “We work with the Metropolitan police, the mayor’s office for policing and crime, the Home Office and community groups to understand this issue and ensure we are able to take action on gang-related content that infringe our community guidelines or break the law.”

Following the removal of the videos, the London drill crew, 1011, set up a petition calling for police to stop banning them from YouTube. Described as a “fast rising collective of young talented musicians,” the group claims they are being targeted by police “with orders to stop their promotional use of YouTube.”